MUNICH - It would certainly be nice if all customers were treated well when they shop in supermarkets. But can supermarket employees also expect to be treated with respect? Recently, in a London branch of the UK's Sainsbury's chain, a checkout lady refused to serve a customer because the employee felt ignored — the shopper was talking on her cell phone the whole time she was putting her purchases on the conveyor belt. The cashier did not begin ringing up the items, saying that she would not do so until the customer got off the phone.

According to British press sources, the customer said: "Apologies, I didn’t realize it was Sainsbury’s policy that you are unable to use your phone at the checkout." The operator replied: "Well, you learn something new every day."

How right she was, at least about the learning thing. But what the incident demonstrates is that supermarket shopping can be a very complex enterprise and requires more skills than merely loading your cart and paying. For example, what do you do if you run into your ex or a gossip-addicted neighbor at the cold cuts counter?

The general rule when no others exist is to fall back on manners and common sense. That sounds great, but it doesn’t always work. So just in case, here are some pointers:

1) Waiting in line is a core component of the food shopping experience. Just bear in mind that the front part of your cart wasn’t designed to ram the person ahead of you in the Achilles tendon. Everybody feels a lot better when personal space is respected, which means keeping a minimum of about 50 centimeters — or about 1.64 feet — between you and the next guy. No, really.

2) That said, the space thing doesn’t mean you can use all those openings in checkout lines to sidle in, pretending you thought that’s where the line ended.

3) If the store opens up another checkout counter as you wait in line, don’t try and beat everybody else standing in front of you to it. Wait at least a few seconds to give people ahead of you the chance to make the change, and then take your place behind them. (If you’re lucky, nobody will notice that another checkout opened and you’ll get to be first, after all.)

4) As unpopular as bumper-car line changers are, customers who park their cart in a checkout line and then with a frenzied "Be right back!" go get the rest of their groceries may be even less so. If you're guilty of this, don’t be surprised when you get back if people have pushed your cart off to the side: You deserve it.

5) Some people feel rejected when the person ahead of them places a divider stick on the conveyor belt to separate their groceries. Please accept that using a divider stick is not a declaration of war. In fact, you should be thankful. But not with too much ebullience please.

6) There’s no time for conversation in supermarkets. There's a job to do. For everyone. So please, just carry on.

7) If you simply can’t avoid getting into a conversation with somebody who doesn't know about rule #6, keep it short. Under no circumstances do you want to be accused of being an aisle-blocker.

8) Sure, take that cube of cheese from the friendly lady in the white food handler hat. The nice bread samples at the bakery counter will go nicely with that cheese, and by all means check out the wine section for whatever they’ve got going there. But please, don’t keep repeating the circuit so that the samples add up to a meal.

9) Unpackaged items like fruit or bread should only be touched if you really intend to buy them. Those who insist on testing the ripeness of the nectarines or kiwis by applying pressure to them should at least — for reasons of hygiene — put a little bag over those squeezy fingers first.

10) And finally, another word about the checkout line: It doesn’t matter how many times on the same day, during the same year or your whole life you’ve been asked, it’s still not OK to answer: "No, I don’t have a goddamned customer card!"